1. Technical Field
The present invention relates to a fuel cell separator and a fuel cell stack including the same, and, more particularly, to a fuel cell separator which can improve a local cooling effectiveness by improving heat transfer efficiency therein, and a fuel cell stack including the same.
2. Description of the Related Art
A fuel cell system typically includes a fuel cell stack for generating electric energy, a fuel supply unit for supplying fuel (hydrogen) to the fuel cell stack, an air supply unit for supplying air (specifically, oxygen which is an oxidant necessary for electrochemical reactions) to the fuel cell stack, and a heat and water control unit for dissipating the reaction heat emitted from the fuel cell stack to outside of the fuel cell system and controlling the operating temperature of the fuel cell stack accordingly.
In the fuel cell stack of the above-configured fuel cell system, through the electrochemical reaction of hydrogen (fuel) with oxygen in air, electricity is generated, and heat and water, as by-products of the reaction, are discharged. The fuel cell stack is formed by continuously stacking a plurality of unit cells, and each of the unit cells includes membrane-electrode assemblies (MEAs) and separators, each being closely disposed on one side of each of the membrane-electrode assemblies.
Here, each of the unit cells is provided with a gasket between the membrane-electrode assembly and the separator w for maintaining a seal and airtightness therebetween. Further, each of the separators is provided with a plurality of manifolds for supplying or discharging fuel and air to or from the membrane-electrode assembly, discharging water (a by-product of the reaction) and circulating a cooling medium therein s (e.g., water).
FIG. 1 is a schematic view showing the cooling flow pattern of a separator of a conventional fuel cell stack including a plurality of manifolds forming channels therebetween, and FIG. 2 is a schematic view showing the temperature deviation between a cooling water inlet and a cooling water outlet of a separator during the operation of a fuel cell stack. From FIG. 2, it can be ascertained that the temperature of the leftmost side of the separator is lowest, the temperature is gradually increased toward the cooling water outlet, and the temperature of the elliptic region of the separator is highest. That is, during the operation of a fuel cell stack, the temperature deviations occur in both lengthwise and widthwise directions. Such a local temperature increase deteriorates the fuel cell stack, thus requiring a solution to the problem.
It is to be understood that the foregoing description is provided to merely aid the understanding of the present invention, and does not mean that the present invention falls under the purview of the related art which was already known to those skilled in the art.